The stuff I have that I consider to be priceless are heirloom pieces.
Pretty much all the necessary items. I've got my great grandfathers hone, a natural combo coti; his vintage strop, linen + horsehide and two of his razors where one of these belonged to his father so my great great grandfather.
It's basically the only stuff I have atm. I feel like I don't need anything else (besides a brush and some cream ;p), I feel so fortunate to have this in my possession.